Yes,
This is a 1,5Gb empty hdf. You can make a copy and add as many as you like. Just copy your WB3.9 BB2 files to it and then you can install the full AKReal on it.
But it's easy to make whatever size you want. Basically you have to know that over 1Gb you have to select "RDB mode".
On WinUAE, "CD & Hard drives" select to "Add Hardfile", then in the lower part where says "New harddisk image file", put the amount of MB you want and click on "Create". Then write a name.hdf for it and finally select in the upper part of the window "RDB mode". Then add the 3.1 Install Disk floppy to "Floppy drives" and (having the new hdf in the upper part of the list of HD's) reboot. Then open the Install 3.1 floppy, HDTools, HDToolbox. Note that HDToolBox, with a right click on it and selecting in the top bar "Icons", "information" has to have in the first line SCSI_DEVICE_NAME=uaehf.device .Then doubleclick on it and then on "Change Drive Type", "Define New", delete "drive definitions" and write "ram:junk" and then click on "Read Configuration", then "Ok", then "Partition Drive", then delete the second partition if you wish and expand the existing one and rename it to DH0 if you like, then "Save changes to drive". When it reboots it will appear as DH0:NDOS, so you quickformat it (also untick Put Trashcan) with the
AmiKit name.
For WinUAE you don't need to use but the default FFS to run OS3.9. If you want something faster you could use SFS or PFS3AIO, but on WinUAE they really work at the same speed.